IMA: create machine owner and blacklist keyrings

This option creates IMA MOK and blacklist keyrings.  IMA MOK is an
intermediate keyring that sits between .system and .ima keyrings,
effectively forming a simple CA hierarchy.  To successfully import a key
into .ima_mok it must be signed by a key which CA is in .system keyring.
On turn any key that needs to go in .ima keyring must be signed by CA in
either .system or .ima_mok keyrings. IMA MOK is empty at kernel boot.

IMA blacklist keyring contains all revoked IMA keys.  It is consulted
before any other keyring.  If the search is successful the requested
operation is rejected and error is returned to the caller.

Signed-off-by: Petko Manolov <petkan@mip-labs.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
index b20cd88..39fd38c 100644
--- a/include/keys/system_keyring.h
+++ b/include/keys/system_keyring.h
@@ -35,4 +35,28 @@
 			      enum key_being_used_for usage);
 #endif
 
+#ifdef CONFIG_IMA_MOK_KEYRING
+extern struct key *ima_mok_keyring;
+extern struct key *ima_blacklist_keyring;
+
+static inline struct key *get_ima_mok_keyring(void)
+{
+	return ima_mok_keyring;
+}
+static inline struct key *get_ima_blacklist_keyring(void)
+{
+	return ima_blacklist_keyring;
+}
+#else
+static inline struct key *get_ima_mok_keyring(void)
+{
+	return NULL;
+}
+static inline struct key *get_ima_blacklist_keyring(void)
+{
+	return NULL;
+}
+#endif /* CONFIG_IMA_MOK_KEYRING */
+
+
 #endif /* _KEYS_SYSTEM_KEYRING_H */